1) How does the production possibilities frontier illustrate scarcity? 2) How does the production possibilities frontier illustrate production scarcity? 3) How does the production possibilities frontier show that every choice involves a tradeoff? 4) How does the production possibilities frontier illustrate opportunity cost? 5) Why opportunity cost a ratio? 6) Why does the PPF bow outward and what does that imply about the relation between opportunity cost and the quantity produced